1. Field of the Invention
The present invention relates to a technique for performing a processing accompanied with heating on a substrate.
2. Description of the Background Art
Conventionally, in various stages of a process for manufacturing a semiconductor substrate, a glass substrate for a display device or the like (hereinafter, referred to simply as “a substrate”), a thermal processing is performed for the substrate, and a rapid thermal process (hereinafter, referred to as “RTP”) is used as a method of thermal processing. In the RTP, by heating the substrate in a chamber with halogen lamps or the like to raise the temperature thereof up to a predetermined temperature in a short time, it is possible to perform processings which have been hard to execute by a conventional long thermal processing with an electric furnace, such as thinning of an insulating film such as an oxide film, suppressing of rediffusion of impurities (or dopants) which are implanted by ion implantation in an activation process, or the like.
In such a thermal processing apparatus as used for the above processing, in order to suppress nonuniformity of the processing on the substrate, proposed is a technique to ensure uniformity of temperature distribution in the substrate during the thermal processing. Another technique is also proposed, which is intended to prevent any processing failure on the substrate by detecting deterioration due to time variation of a plurality of lamps or the like. Japanese Patent Application Laid Open Gazette No. 11-135449, for example, discloses a technique to ensure uniformity of heat distribution in the substrate while early detecting deterioration of lamps by providing a plurality of lamps which are individually controlled in a light emitting part having a multilayer mirror structure consisting of hemispherical reflection mirrors of various sizes and providing photosensors for monitoring the amount of outgoing lights from each of the lamps between each pair of adjacent reflection mirrors.
Japanese Patent Application Laid Open Gazette No. 2002-357660 discloses a calorimeter for converting light energy absorbed by a black body in a sensor into an electrical signal which has a property of fast response, thereby responding a short radiation pulse.
In the thermal processing apparatus using lamps, there is a possibility of reducing light energy which would reach a surface of the substrate due to deterioration of the lamps, stains and dirt on windows of a chamber through which light enters or the like. Especially, in recent, also proposed is a technique to heat the substrate in a shorter time by using flash lamps as a heat source for the substrate and in a thermal processing apparatus using flash lamps, there may be a case where organic substances or the like floating in the air are carbonated by a flash of the flash lamps to be deposited onto surfaces of the windows in the chamber.
The reduction in light energy going into the chamber due to the stains and dirt on the windows of the chamber can not be grasped by monitoring the energy of light going out from the lamps near the lamps. Since the irradiation time of the flash lamps is extremely short and it is therefore impossible to measure the light energy with high accuracy by a method of using a generally-used photosensor, a method of monitoring infrared rays passing through the substrate, a method of calculating the spectral distribution on a surface of the substrate or the like, it is hard to detect deterioration and a breakdown of the flash lamps due to time variation or the like. In a case where a processing for a substrate is performed with the energy of light emitted into the chamber lowered, there arises a possibility of causing a failure in the processing for a substrate.
On the other hand, in the thermal processing apparatus using the flash lamps, since heating for a substrate is performed in an extremely short time, it is disadvantageously difficult to measure a surface temperature of a substrate during thermal processing in real time.